SC1486A Datasheet, PDF (19/29 Pages) Semtech Corporation – Dual Synchronous Buck DDR and DDR2 Power Supply Controller

SC1486A
POWER MANAGEMENT
Application Information (Cont.)
Layout Guidelines (Cont.)
The layout can be considered in two parts, the control section referenced to VSSA1/2 and the power section.
Looking at the control section first, locate all components referenced to VSSA1/2 on the schematic and place
these components at the chip. Connect VSSA1 and VSSA2 using either a wide (>0.020”) trace or a copper pour if
room allows. Very little current flows in the chip ground therefore large areas of copper are not needed.
5VSUS
VCCA1
VCCA2
R1 10R
0402
R2 10R
0402
PWR_SRC
1.8V
C17
R10
27p 45k3
0402 0402
VSSA1
R13
17k4
0402
C8
1u
0603
R3
1M
PGD1
VCCA1
C20
1n
0402
TON1
VCCA1
C21
1u
0603
U1
3 _VDDP1
1 _PGND1
6 _DH1
7 _BST1
5 _LX1
4 _ILIM1
2 _DL1
27 _PGD1
22 _EN/PSV1
24 _VOUT1
26 _FB1
23 _TON1
25 _VCCA1
28 _VSSA1
5VRUN
PWR_SRC
SC1486A
VDDP2 ¹⁷
PGND2 ¹⁵
DH2 ²⁰
BST2 ²¹
LX2 ¹⁹
ILIM2 ¹⁸
DL2 ¹⁶
PGD2
13
FB2
12
REFIN ⁸
REFOUT ¹⁰
TON2 ⁹
VCCA2 ¹¹
VSSA2 ¹⁴
C9
1u
0603
PGD2
REFOUT
TON2
VCCA2
C22
1u
0603
R4
649k
0402
C23
1n
0402
R11 10R
0402
C18
1u
0603
C19
0u1
0402
1.8V
R9
R12
10k0
0402
10k0
0402
0.9V
VSSA2
Figure 7: Components Connected to VSSA1 and VSSA2
Figure 8: ExampleVSSA Copper Pours (Left) and 0.020” Traces (Right)
 2004 Semtech Corp.
19
www.semtech.com